With the widespread popularity of portable communication devices such as cellular telephones, there has been an increasing demand for such portable communication devices to operate in more than one user mode. In a first mode of operation, here referred to as a normal-phone mode, a user first holds the portable communication device away from his ear and enters access information such as a telephone number. The user inputs can be verified by monitoring the information shown on a display. The user then places the portable communication device close to his ear to engage in a call.
The first mode of operation limits usability; the display cannot be seen and the user cannot input information while the portable communication device is next to the user's ear. In addition, it is sometimes desirable for the user to not have to hold the portable communication device while engaged in a call. The user may thus want to place the portable communication device down while still maintaining communication. For these reasons, a second mode of operation, a hands-free or speakerphone mode, is employed.
In the speaker phone mode, the portable communication device will emit audio information at a louder volume, thus allowing the user to hear information while the portable communication device is away from his ear. If, however, the portable communication device is in the speakerphone mode while it is next to the user's ear, damage to the user's hearing system could result. Therefore, mode switching reliability between normal-phone mode and speakerphone mode is important to ensure that the portable communication device does not inadvertently switch to the speakerphone mode while it is close to the user's ear.
One method to prevent the portable communication device from operating in speakerphone mode while it is close to a user's ear is through the use of a proximity detection system. The proximity detection system senses when the user's head is close to the portable communication device and causes the normal phone mode to be initiated. However, use of a conventional proximity detection system must contain sophisticated reliability circuitry in order for the system to be fail-safe.
Accordingly, there is a need for a highly reliable apparatus and method to switch between private-mode and speakerphone mode in a portable communication device. The result would be a portable communication device that could safely be switched between the private-mode and speakerphone mode, thus allowing greater use and functionality of the portable communication device.